1. Field of the Invention
This invention relates generally to fire protection, prevention and fire extinguishing and explosion suppressing compositions and methods, and more particularly to fire protection, prevention and fire extinguishing and explosion suppressing compositions and methods using variable viscosity breakable gelled water formulations that hold a layer of water of desired viscosity and thickness where placed but then is easily removed by the application of a second powdered or water based component that breaks the gel so it becomes free flowing and is easily rinsed away.
2. Background Art
In addition to being inexpensive and usually readily available, water has the advantage of its capacity to deprive fires of oxygen as well as its high heat transfer capacity so it quickly and efficiently cools the fuel below their combustion temperature. Water is relatively inexpensive and it is usually easy to deliver to the fire while firefighters remain at safe distances. For these and other reasons water endures as an important fire control and extinguishing agent.
Although the efficiency of water as a fire extinguishing agent is well known, it has serious drawbacks. Water quickly and easily gravitates off surfaces to which it is applied and therefore may not have smothered the fire or cooled the burning material to below its fire point. Water that immediately runs off a surface offers only limited cooling and most of the potential water use advantages are quickly lost as the water drains away. Liquid water rapidly drains away with any remainder quickly evaporating from a heated surface. Liquid water must be continuously applied to effectively cool a hot surface. Flooding with large quantities of water has another major drawback that can add significantly to the collateral damage of fire fighting—not only the water damage itself but also by spreading any contaminants that may have been present at the site of the fire.
Three things are required for fires to occur and continue, also known as a “fire triangle”. They are: (1) the presence of a flammable material, (2) air (oxygen), and (3) sufficient heat to raise the temperature of the fuel above its fire point. An initial spark or igniter is usually required to start a fire.
Due in part to availability, the least costly method to suppress fires is to use water to deprive a fire of oxygen and, at the same time, lower the combustion threshold thereby removing two sides of the theoretical fire triangle; the fuel and an ignition source may still be present. In addition to smothering fire, depriving it of oxygen, keeping water in continuous contact with burning or hot fuel will cause rapid cooling. Water efficiently absorbs heat and therefore lowers the heat level of most fuels to below their flash point and fire points. The fire point is the minimum temperature at which a fuel will continue to burn without additional application of external heat.
Liquid water is 30 times more efficient than air in cooling. Scientifically, the heat transfer coefficient of air is 0.02 W/m2K and the heat transfer coefficient of water is 0.6 W/m2K where W=watts, m2=square meters, and K=degrees Kelvin. Since 0.02 is 1/30 of 0.6, the cooling efficiency of liquid water is thirty times that of air. But this applies only if the water is and remains a liquid; the material is cooled only from the boiling point of water downward to the temperature of the applied water.
The vast majority of the cooling efficiency of water in fire fighting is due to fuel heat removal that occurs when water is converted from liquid to vapor, from a fluid into steam. The basis for this effectiveness is the latent heat of vaporization of water. The latent heat of vaporization (or more properly, the standard enthalpy change of vaporization, ΔvH⊖) is the amount of energy required to transform a given quantity of a liquid into a gas (e.g., water into steam). When water is heated to its boiling point, tremendous additional heat is required to then convert the liquid water to water vapor at the same temperature. Raising the temperature of one gram of water one degree C. requires one calorie. At 100 degrees C. (212° F.) an additional 540 calories are then required transform that same gram of liquid water to steam, still at 100 degrees C. As the water vaporizes, heat is instantaneously carried away thus rapidly cooling the fuel. When the fuel is sufficiently cooled, it will not support a flame; the fire ceases and re-ignition will not occur.
This phenomenon is obvious as one observes the changes in color of the smoke emanating from most fires when sprayed with water. Smoke is an air suspension of small particles that result from the incomplete combustion of a fuel—the incomplete oxidation of a carboniferous fuel to carbon dioxide and water. Carbon is seen as soot, either in black rising microscopic particles of smoke or in falling flakes, etc. When water contacts the fuel, the color of the rising “smoke” almost instantly turns white. However, this “white smoke” is not typical smoke but is steam (vaporized water). As the steam rises, it carries vast amounts of heat away thus efficiently lowering the fuel temperature.
This sequence is much like the series of events which occur when a piece of red hot steel is immersed in water. There is an instant production of hot steam which almost instantly lowers the temperature of the metal to the boiling point of water as the liquid water is converted to steam which then carries the heat into the atmosphere. As long as sufficient water remains present, further cooling continues at a slower rate until the metal reaches the temperature of the surrounding water.
Von Blucher, U.S. Pat. No. 5,190,110 addressed some of the disadvantages of using liquid water by using absorbent polymers with particle sizes from 20 to 200 microns dispersed in a water miscible media to be incorporated into the water by stirring or pumping thereby producing thickened water for fire control. Much time is required for the polymer particles to absorb water and swell whether the solid granules are pre-mixed or added directly in advance of the nozzle while they are in the non-swollen condition. In the aqueous system taught by von Blucher, from 50% to 80% by weight, preferably from 60% to 70% by weight, of the overall amount of water is present in the swelled particles. Following their use in fire fighting or prevention, the accumulations are difficult to remove during the cleanup operations and can add significantly to the cleanup damage and costs.
Von Blucher, U.S. Pat. No. 4,978,460 discloses a process of using solid polymer particles encased by a water-soluble release agent to avoid agglutination of the particles. These solid granular particles may take from ten seconds to several minutes to expand; far too long to be practical due to the limited time it takes for the water to pass through a fire hose. This von Blucher patent also requires large quantities of the relatively expensive thickening agents to achieve good results. Furthermore residual accumulation of these thickening agents causes cleanup complications once the fire is extinguished. Although extinguishing fires is the most critical aspect of the fire fighter's responsibilities, cleanup following the dousing of the fire is also a major concern.
Zweigle, U.S. Pat. No. 3,758,641 discloses the use of solid granular polymer particles with high water absorption for fire extinguishing purposes but this process is best accomplished with highly specialized fire fighting equipment and the applied material is difficult to remove once applied. This method also leaves high concentrations of contaminants after the fire has been controlled.
Buil, U.S. Pat. No. 5,518,638 discloses the use of thickened amorphous silica in water as a fire extinguishing and protective agent. Silica simply thickens water but water so thickened does not withstand rapid evaporation in the presence of the heat of the fire. The residual is very difficult to remove from the surfaces it contacts, especially when somewhat or completely dried; this adds significantly to cleanup.
Reed, U.S. Pat. No. 6,776,920 discloses the use of a heat absorbing water based material for fire fighting and other uses. This material requires the use of two different formulations which are passed through magnetic fields to formulate the final product. The resultant applied gel is not easily removed or breakable.
Hicks et al, U.S. Pat. Nos. 5,989,446 and 6,245,252 disclose a method for applying for applying polymer particles to a surface to combat fires using cross-linked, water-swellable polymer particles made by inverse phase polymerization reaction in the form of a water-in-oil emulsion. This water-absorbent combination is added to fire fighting water in amounts sufficient to increase the viscosity of the water-additive mixture. Although these formulations result in increased viscosity water that has some fire protective capacity, they are composed simply of a polymer in a water-in-oil emulsion.
Inverse phase polymerization reactions and emulsions are well known. Those skilled in the art know this is usually done in a water/oil emulsion as in the Hicks et al '446 and '252 patents. The emulsion enhances even distribution of the polymer but delays viscosification. Also, spraying oils on fires in an attempt to suppress a fire is not usually recommended by firefighters both because of the potential for ignition of the hydrocarbon and also the potential for release of toxic volatile organic compounds from the heated hydrocarbons. Emulsifiers are essential in the '446 and '252 patents and in similar patents to produce the inverse phase polymerization reaction required to produce the carrier water/polymer or water/oil end product with the polymer in the internal phase.
Unlike the Hicks et al patents '446 and '252 and similar patents that require emulsifiers and oils to produce the inverse phase polymerization reaction, the present invention employs water soluble cross-linked polyacrylic acid polymers, therefore no emulsifiers or oils are required and there is no swelling of an oil encapsulated water/oil internal phase
The Hicks et al patents '446 and '252 and previously patented thickened water products are also relatively stable with characteristics that make them difficult to remove when the fire is suppressed and the fire danger has passed. Fire damage is furthered by accumulations of the applied materials plus the subsequent water damage resulting from the high volumes of water required to flush away the applied materials.
Our previous patent, U.S. Pat. No. 6,201,050, which is hereby incorporated by reference herein in its entirety, discloses a viscous breakable gel additive carrier for mixing with ion containing materials, including dry powder based and calciferous materials, which in its uniform homogeneous gel form, prevents separation and settling of the additives prior to mixing, and upon mixing with the ion containing materials liquefies and becomes totally and evenly miscible to allow easy and precise mixing. The gel includes formulations of selected additives thoroughly mixed with a cross-linked polyacrylic acid gelling agent, an organic chelating agent, and an alkaline electrolyte to produce uniform homogeneous mortars, grouts, stuccos and other compositions.
The present invention relates to fire protection, prevention and fire extinguishing and explosion suppressing compositions and more particularly to variable viscosity water formulations composed of breakable gelled water which acts to hold a layer of water of desired viscosity and thickness where placed but then is easily removed by the addition of a second powdered or water based component that breaks the gel so it becomes free flowing and is easily rinsed away.